import com.fasterxml.jackson.databind.ObjectMapper;
import com.mysql.jdbc.jdbc2.optional.MysqlDataSource;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.sql.DataSource;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;



@WebServlet("/message")
public class MessageServlet extends HttpServlet {

    private ObjectMapper objectMapper = new ObjectMapper();
//    private List<Message> messageList = new ArrayList<>();
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //显式声明当前的响应数据格式
        resp.setContentType("application/json;charset=utf8");
        //把messageList 转成 json 字符串， 并且返回给页面就行了
        List<Message> messageList = null;
        try {
            messageList = load();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        resp.getWriter().write(objectMapper.writeValueAsString(messageList));
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取到body中的数据并解析
        Message message = objectMapper.readValue(req.getInputStream(), Message.class);
        //把这个message保存一下，简单的方法就是保存在内存中
//        messageList.add(message);
        try {
            save(message);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        resp.setStatus(200);
        System.out.println("提交数据成功：from="+ message.getFrom()+", to="+message.getTo()+", message="+message.getMessage());
    }
    private List<Message> load() throws SQLException {
        //从数据库查询数据
        //1.先有一个数据源
        DataSource dataSource = DBUtil.getDataSource();
        //2.建立连接
        Connection connection = dataSource.getConnection();
        //3.构造SQL
       String sql = "select * from message";
        PreparedStatement statement = connection.prepareStatement(sql);

        //4.执行SQL
        ResultSet resultSet = statement.executeQuery();
        //5.遍历结果集和
        List<Message> messageList = new ArrayList<>();
        while(resultSet.next()){
            Message message = new Message();
            message.setFrom(resultSet.getString("from"));
            message.setTo(resultSet.getString("to"));
            message.setMessage(resultSet.getString("message"));
            messageList.add(message);

        }
        //5.关闭连接
        statement.close();
        connection.close();
        return messageList;
    }
    private void save(Message message) throws SQLException {
        //把数据保存到数据库中



        //1.先有一个数据源
        DataSource dataSource = DBUtil.getDataSource();
        //2.建立连接
        Connection connection = dataSource.getConnection();
        //3.构造SQL
        String sql = "insert into message values(?,?,?)";
        PreparedStatement statement = connection.prepareStatement(sql);
        statement.setString(1,message.getFrom());
        statement.setString(2,message.getTo());
        statement.setString(3,message.getMessage());
        //4.执行SQL
        int ret = statement.executeUpdate();
        System.out.println("ret = " +ret);
        //5.关闭连接
        statement.close();
        connection.close();
    }


}
